Individual rows may be updated via their Result object in one of two ways.
You can create an object representing an existing database table row and hold it in your programmes memory,
passing it around from function to function changing its values,
before actually updating the contents into the database.
This is a delayed update.

A direct update still involves fetching the existing row from the database,
but instead of storing new column values in the Row object,
the update method is called and passed the set of new values to store in the table.

NOTE: Running a direct update on a row object that already has changed values,
will *also* apply those values to the database.
If values are changed both on the object,
and in the update method arguments,
the argument values take precedence.

$fred_user's contents can now be changed using the accessor methods created by add_columns, back in CREATE. These are generally named after the columns in the database, so to change fred's real name, use the realname method.

The update method will only actually send an UPDATE statement to the database if one or more of the columns have changed. The internal tracking of which columns have been changed can be queried using several methods. is_changed returns true (or a list of changed column names), if any column values have changed. is_column_changed will return true or false for the given column name argument. The previous values of the columns are not stored.

To update a whole set of rows, or all of them, we first need to create a ResultSet object representing the query conditions that would be needed to select that same set of rows. We need to use search, then we use the update method on the ResultSet.

A transaction is issued containing two statements, a SELECT and then either an INSERT or an UPDATE depending on the results.

Do not use this method if you definitely don't have either the primary key, or a unique index value available. The find method used under the hood will probably not do what you expect. In this case, manually run a separate search method call to check for existance, and then call create.